Installation and Reference Guide HP AdvanceStack 100Base-THub-12TX, Hub-12TXM, and Switch Modules 1997-06

HP Hub-12TX/Hub-12TXM Installation and Reference Guide
A-4 Troubleshooting
Physical Configuration
If problems occur after altering the network configuration,
restore the original connections, and try to track the problem
down by implementing the new changes, one step at a time.
Ensure that cable distances and other physical aspects of the
installation do not exceed 100Base-TX specifications (refer to
Chapter 2).
System Integrity
As a last resort verify the hub’s integrity with a power-on reset.
Turn the power to the hub off and then on several times. If the
problem still persists and you have completed all the preceding
diagnoses, then contact your HP-authorized reseller for further
assistance. (Refer to Appendix E.)